The Condon arrangement provides two separate essentially matching toroidal magnetic cores with line circuit windings, control circuit windings, sense windings, and feedback windings. Line current flowing in the line windings causes in the two cores essentially equal amounts of the same polarity of line current magnetizing intensity H. A pulse of control current flowing in the control windings causes corresponding changes in the two cores of control current magnetizing intensity H where the changes of control H in the two cores are of essentially equal amounts of control H but of the opposite polarity. Each change of control H causes the magnetic inductions B in the two cores to undergo corresponding changes from an amount of one polarity of B corresponding to a zero amount of control H to B saturation of the same polarity of B and then from B saturation back to an amount of the same polarity of B corresponding to a zero amount of control H. These changes of B in the two cores occur along minor saturation hysteresis loops. The changes of B in the two cores produce induced voltages in the sense windings which are connected in series opposition with regard to polarity of the induced voltages. With no line H present in the two cores, the output of the series connection of sense windings is essentially zero voltage since the changes of B in the two cores are essentially of equal amounts of opposite polarity. The presence in the two cores of line H, due to the flow of line current, causes the changes of B in the two cores to differ by an amount which is a measure of the amount and polarity of line H (and thus a measure of the amplitude and polarity of line current). Such a difference in the changes of B in the two cores produces a voltage pulse, the amplitude and polarity and duration of which are a measure of the difference between the amounts of polarities of the changes of B in the two cores. A succession of voltages pulses is cumulatively and algebraically integrated to provide a changing output voltage, and amplitude and polarity of which are a measure of the cumulative integration. The output voltage is used to cause in each core, by means of either the sense windings or the feedback windings, an amount of feedback H where the amount is according to the output voltage and the polarity opposes any line H in the two cores. The output voltage becomes essentially constant when the feedback H essentially cancels the line H in the two cores and the amplitude and polarity of the constant output voltage are a measure of the amplitude and polarity of line current.
While the Condon arrangement is quite satisfactory from an operational standpoint, it requires two cores which are essentially matched. It is an advantage to circuit designers and to magnetic structure designers not to be required to contend with the necessity for such matching.